A 1970 Gibbs spring reverb tank (2 spring model) was sampled 14 times. This was probably taken from a Hammond organ, but the same model was used in Fender gear also. Different hardware setups were used, along with a little digital and analog trickery (in some programs), to get a variety of tonal possibilities, all still true to the basic spring sound. In some cases, feedback was used (with 2 different paths), in others cassette tapes were used, and in some cases objects were placed on or wedged between the springs to cause different resonances and decay behaviors. Some employed a method to shift the frequency response of the spring up or down. Check the manual for detailed descriptions of how each effect was made.
Besides tonal variety, another main idea behind this set was to provide DISTORTION. This is because I’ve always liked distorted reverb. To this end, each sampled effect is available in 1k and 6k options. The 1k can be used for clean reverb, and the 6k ones for thicker or fully distorted verb. In some cases, the distortion can be mixed in and used to provide an all new element to a sound, making these useful for sound mangling purposes.
As you could imagine, a 6k reverb program at around 5 seconds would be quite taxing on any CPU (especially at 96khz). Keep in mind though, there is plenty of value just in the tonal variations/colors of reverb available, which can be used without the distortion kernels by using the 1k versions. There are also long and short presets for each effect, so you can quickly audition each by loading the short 1k versions until you find a color you like, then switch to the longer 6k versions at some point down the road (or not if you don’t need them).